In total , the XR-5M15 demonstrated a series of forty three hot fire tests at our Mojave facilities. Applications for the 5M15 include returning manned space vehicles from Lunar orbit and Mars to the Earth, and performing in-space maneuvering.

The approach was a rapid design, build and test of a workhorse main engine based closely on relevant design features from our previous engine programs. The 5M15 program built upon XCOR's existing 3M9 LOX/methane engine, as well as our 1,800 lbf 4K5, 10,000 lbf 5M12 design, and 400 lbf 4A3 EZ-Rocket engines.

This main engine development uses several features from the 3M9, including the same augmented torch electrical ignition system and the propellant combination.

Relevant features of the 4K5 engine include the igniter geometry, the torch spark igniter, and the fuel cooling configuration. While the 5M15 uses many of the same 4K5 component designs, we changed the fuel, lowered the chamber pressure, and increased the size.

Our 5M12 engine study is the closest configuration of the main engine. It was developed for a DARPA program through to layout design, but never built. The DARPA contract enabled us to develop the methane cooling analysis tools, which have also been used with the 3M9 engine runs.

The 5M15 engine has many relevant features in it that are shared with XCOR’s FAA licensed manned vehicles, the EZ-Rocket and the X-Racer.

The workhorse engine served several purposes. It validated the key engine design elements, including the regeneratively cooled chamber/throat assembly, the stability and performance of the injector, and the reliability of ignition. It incorporated a number of design features for safety and reliability, critical for human-rated application, that were demonstrated on previous XCOR engine designs. Finally, it is a modular design, which facilitated rapid test of new components during development, and enabled modification for future NASA Exploration applications.